冲击荷载作用下岩石峰后损伤破坏特性研究

发布时间：2019-01-27 13:40

【摘要】：摘要：本文以异形冲头SHPB动态测试系统为平台,结合高速摄像技术,对花岗岩在不同冲击速度下的峰后破坏特性进行了研究,并建立异形冲头SHPB测试装置的PFC2D数值模型,在细观层面上进一步对岩石在冲击荷载作用下峰后阶段的裂隙产生、扩展以及损伤等进行了研究。主要研究内容及成果如下： (1)随着冲击荷载的逐渐增大,岩石动态应力应变曲线的峰后变形由弹性逐渐向延性过渡,其峰后变形模式分为弹性回弹、脆性破坏和延性变形。三种峰后变形模式对应着岩石三种破坏形态,分别为：端部环状剪切带、环状劈裂破坏和粉碎破坏； (2)试样表面的裂纹扩展方向与试样冲击加载方向平行,且明显的宏观裂纹主要发生在峰后阶段,岩石试样在冲击荷载作用下的最终破坏形态主要由两个方向上的破裂带控制：一是试样侧面沿轴向的劈裂带,二是试样端部与杆接触面的环状破裂带。； (3)PFC数值分析发现,冲击荷载作用下,岩石的变形破坏过程由剪切裂纹和拉伸裂纹共同控制。在峰前的弹性变形阶段以剪切裂纹为主,当岩石进入非线性变形阶段,拉伸裂纹才开始出现；岩石在峰后阶段的剧烈破坏则是拉伸裂隙主导的劈裂破坏。 (4)基于Weibull分布的动态统计损伤模型能较好的描述岩石的动态变形过程,且充分反映了岩石强度、应变和加载应变率之间的关系。同时,试样的损伤演化可以用微裂隙累积增长来表征,损伤和微裂纹之间具有很好的线性相关性。
[Abstract]:Abstract: based on the SHPB dynamic testing system of special-shaped punch, combined with high-speed camera technology, the post-peak failure characteristics of granite at different impact velocities are studied, and the PFC2D numerical model of SHPB testing device for special-shaped punches is established. The crack generation, propagation and damage in the post-peak stage of rock under impact load are further studied at the meso level. The main research contents and results are as follows: (1) with the increasing of impact load, the post-peak deformation of dynamic stress-strain curve of rock changes gradually from elasticity to ductility, and the post-peak deformation mode is divided into elastic springback. Brittle failure and ductile deformation. The three post-peak deformation patterns correspond to three failure patterns of rock, which are end annular shear zone, annular split failure and comminuted failure. (2) the crack propagation direction on the specimen surface is parallel to the impact loading direction of the specimen, and the obvious macroscopic crack mainly occurs in the post-peak stage. The ultimate failure pattern of rock specimen under impact load is mainly controlled by the fracture zone in two directions: one is the axial fracture zone on the side of the specimen, the other is the annular fracture zone on the interface between the end of the specimen and the bar. (3) PFC numerical analysis shows that the deformation and failure process of rock under impact load is controlled by both shear crack and tensile crack. Shear cracks are dominant in the elastic deformation stage before the peak, and tensile cracks only begin to appear when the rock enters the nonlinear deformation stage, and the sharp failure of the rock in the post-peak stage is the splitting failure dominated by the tensile fracture. (4) the dynamic statistical damage model based on Weibull distribution can well describe the dynamic deformation process of rock, and fully reflects the relationship among rock strength, strain and loading strain rate. At the same time, the damage evolution of the specimen can be characterized by the cumulative growth of microcracks, and there is a good linear correlation between the damage and the microcrack.
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45

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